Laminated magnetic circuit structure for transformers



C. H THORDARSON.

LAIYHNATED MAGNETIC CIRCUIT STRUCTURE FOR TRANSFORMERS. APPLICATION FILED FEB. 3, 1916.

1,406,245; Patented Feb. 14, 1922.

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CHESTER H. THORDARSON, OF CHICAGO, ILLINOIS.

LAMINATED MAGNETIC CIRCUIT STRUCTURE FOR TRANSFORMERS.

To all whom it may concern:

Be it known that I, CHESTER H. THORDAR- SON, a citizen of the United States, and a resident of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Laminated Magnetic Circuit Structures for Transformers; andI do hereby declare that the following is a full, clear, and exact description thereof, reference being had to the accompanying drawings, and to the characters of reference marked thereon, which form a part of this specification.

This invention relates to improvements in laminated magnetic circuit structures for transformers and like electro-magnetic devices and the invention consists in the 'combination and arrangement of the parts shown in the drawings and described in the specification and pointed out in the appended claims.

Among the objects of the invention is to reduce the costs of such magnetic circuit structures, both by reason of a reduction of the metal employed and by reason of the ease of assembling the plates and therefore the reduction 1n time re uired for assembling.

A further object o the invention is to provide a novel means of producing and maintaining good magnetic abutting joints of the laminm of a character to enlarge the abuttin contact of said members relatively to their transverse dimensions and to minimize magnetic reluctance at such joints without the necessity of interleaving alternate laminae or groups of lamin as has heretofore been common; to provid such a joint as will prevent shifting of the laminae in their planes and to provide such a joint which, while fulfilling the desirable functions referred to, has the effect to materially avoid reduction of the cross section of the circuit members and, to a maximum extent, avoid crowding of the magnetic lines of force at said joints. A further object of the invention is to provide a saw-tooth abutting joint for the laminae of the magnetic circuit structure of such form as will enable the saw-tooth projections to be exactly duplicated at all the joints and to thereby insure accurate abutting fit of the projections and corresponding recesses of the members, and further to provide interfitting abutting joints in which the salients or tooth-like projections ofone member fit into the corresponding depressions of the other member so as to insure Specification of Letters Patent.

Patented Feb. 14, 1922. 3, 1916. Serial No. 75,969.

the parts being forced or drawn into intimate contact throughout the length of their angular abutting faces, the angle of the teeth and sockets being for this purpose made relatively small or acute.

Other objects of the invention are to otherwise improve and simplify magnetic circuit structures for transformers and other electro-magnetic devices, as will appear from a fuller disclosure of the inventionwhich follows.

In said drawings vFigure 1 is a vertical section of a magnetic circuit structure for a shell type transformer on the line 11 of Figure 2 showing a portion of the binding and supporting frame.

Figure 2 is an enlarged fragmentary edge elevation thereof.

Figure 3 illustrates the elements of a magnetic circuit structure for a core type transformer.

Figure 4 illustrates another form of magnetic circuit structure for a shell type transformer.

Figure 5 is a fragmentary detail showing, slightly separated, the toothed and indented abutting edges of two cooperating laminae of the magnetic circuit structure.

Figure 6 is an enlarged detail of the sawtooth abutting joint.

Figure 7 is an enlarged sectional view of a roup of abutting laminae.

11 Figure 1 I have shown in a somewhat diagrammatic manner the elements of a magnetic circuit structure for a shell type transformer, wherein 10, 11, designate, respectively, the top and bottom members of the structure, 12, 12, the end members, and 13 the central or core member thereof. The

said laminated end members and the core member are provided at their ends with numerous relativelysmall, symmetrically dimensioned, pointed projections or saw teeth 14 (Figure 5) which enter correspondingly shaped depressions 15 in the proximate edges of the laminae of the top and bottom members of the circuit structure to form irregular elongated magnetic joints between the laminae of the circuit structure. The said depressions 15 of the top and bottom members are located within the inner or proximate edges of the laminae of said members, and may be said tov be sunk within said inner or proximate edges, whereby the abutting edges of the laminae of said top and bottom members are formed with a minimum wastage of material to produce said depressions.

In accordance with onephase of my invention there are a plurality of such saw tooth projections and recesses in the abutting edges of the laminae,-and said projections and recesses are symmetrical with respect to each other. That is to say the teeth or projections and the corresponding recesses of all the joints are of like dimensions and shape so that an end member or a core member may be abuttingly fitted to a top or bottom member regardless of which end of the end or core member is presented thereto, or regardless of which side of the plate or laminae faces upwardly. By thus making the said saw teeth or projections and corresponding recesses or depressions symmetrical with respect to size and angular dimension, the cutting of the laminae is fa.- cilitated, inasmuch as all of the plates which are end cut or saw toothed may be cut by the use of the same dies, and the top and bottom members may be made duplicates of each other and therefore also cut .by the same .dies. A further advantage of this latter feature of my invention is that, inasmuch as no special observation of the cut ting or shape of the parts is required when assembling, the assembling of the magnetic circuit structure is greatly facilitated and the cost of the assembling operation is thereby materially. reduced.

It is a further feature of my invention that the saw-tooth projections and recesses shall be made with relatively sharp angles and shall also be made relatively shallow, as compared to the transverse dimensions of the laminae against which it abuts. So far as I have determined in practice the best results are secured by making the said saw tooth projections and corresponding recesses with their sides spaced at from to degrees apart and, although I do not limit myself to this particular range of angular dimensions the same is recommended.

I have found that by making the sawtooth projections relatively sharp, said projections and recesses fit more intimately than if the same be made of larger angular dimensions, so that thereby I am able to provide a magnetic joint having a long area of abutting contact with a minimum degree of magnetic reluctance. This character of magnetic joint is especially desirable when used in magnetic circuit structures wherein the weight of the material in the completed 69-structure acts in the direction of the longer axes of the saw-tooth projections to tend to force the irregular abutting surfaces together, as shown in the construction in Figure 1. In said figure the V-shaped depressions 15 are. formed on the proximate,

or lower and upper sides, respectively, of the top and bottom members 10, 11, respectively, and the saw-tooth projections on the members 12 and 13 extend from the end edges thereof in vertical direction. In such an arrangement the force of gravity acts in conjunction with the magnetic pull on the abutting mem bersafivhen the exciting current is turned on, to draw or force the duced from 10 to 12 per cent. This arrangement is also advantageous inasmuch as the vibration of the circuit members, when the transformer 18 energized, has a like effect to force the irregular surfaces into abutting:

contact.

A further advantage of forming the abutting edges of the laminae of the circuit struc-, ture members with a. plurality of relatively short, sharp, tooth-like projections and opposing indentations or recesses is that the cross-section of the laminae of the members which bear the indented or sunken irregular abutting edges, to-wit, the top and bottom members 10 and 11, as herein shown, may be kept within such cross-sectional dimensions as to avoid crowding of lines of magnetic force at the abutting magnetic joints and thereby provide good permeability.

The laminae may be clamped together be tween angle bars 16 in the general manner shown in the pending application for United States Letters Patent of Robert A. Connor, Serial No. 36,655. In this arrangement clamping bolts 17 extend between corresponding parallel members 18 of the angle bars, which latter members bear against the opposite side faces of the grouped laminae forming the circuit structure. The other members 19 of the angle bars may cooperatewith the transformer winding in the manner shown in said Connor application, in the event of the useof interspersed windings wit-h an alternatev disposition of high and low tension winding units. It will be understood, however, that the circuit structure binding frame may be otherwise constructed. A further feature of my invention, whatever the character of the laminae binding frame, and which cooperates with the irregular or saw-tooth abutting edges of the laminae, lies in the provision of recesses 20 in the top and bottom members 10 and 11, or the edges thereof opposite to' the sunken indentations 15 which are engaged'by the saw-tooth proections 14 of the end and core members 12 20, serves to prevent shifting or displacement of the laminae in their planes, not only of the said top and bottom members, but also of the end and core members of the circuit structure.

In order that the serrated or toothed abutting edges of the laminae may be maintained in a maximum intimate contact with each other wedging means may be employed which act on the laminae to hold the abutting edges thereof closely together. When employing the frame structure herein shown the wedging means may consist of wedges 22 which are adapted to be forced between flattened faces of sleeves 23 and the ends. of elongated openings in the angle frame bars through which the bolts extend, the sleeves surrounding the bolts exterior to the flanges 18, and being made of a diameter as large as the heads and the nuts of the clamping bolts 17.

In Figure 3 is shown a magnetic structure for a core type transformer, wherein 25 designates the core, 26, 26; the end members and 27 the bottom members. In this construction the laminae of the core and bottom. members are provided with V-shaped indentations and the end pieces are provided with saw-tooth projections abuttingly engaging the same. The laminae of the core and bottOll1| members may likewise be providedon their edges remote from the lndentations with curved recesses 30 to receive the clamping bolts, not shown.

In Figure 4: is shown another form of magnetic circuit structure for shell type transformers, wherein 35 designates the core member, 36, 37, the top and bottom members, respectively, and 38, 38, the end members, the laminae of each end member abutting at one end against the side edge of the laminae of the core member and at their other end against the laminae of either the top or the bottom member of the circuit structure. The upper and lower. edges, respectively, of the laminae of the top and bottom members are provided with recesses 39 to interlock with the clamping bolts whereby the laminae are prevented from shifting in their planes. In this construction, as in those previously described, the longer axes of the tooth-like projections of the abutting magnetic joints of the laminae extend in a direction parallel to the direction in which gravity acts to maintain the interfitting abutting joints of the laminae of the circuit members in intimate contact.

For the sake of clearness of illustration of the invention, the windings have been omitted, but it will be understood that the present improvements are capable of adaptation with various forms of windings.

From an inspection of Fi res l, 3, 4 and 5 it will be noted that the in entations of the top and bottom members are formed within the lines defining the inner edges of the laminae thereof, so that the only material wasted in cutting the laminae is that represented by the dimensions of the triangular or V-shape indentations. Furthermore, by reason of the fact that the indentations of the laminae are symmetrical with respect to dimensions and location, the lamina of the top and bottom members are accurate duplicates. Therefore, said top and bottom laminae may be cut by the same die.

In practice, I have found it to be desirable to make the points of the teeth somewhat less sharp than the angular bottoms of the V-shaped indentations, as shown in Figure 6, inasmuch as, in this manner, the edges of the teeth and of the indentations may be made to fit in very intimate contact with each other throughout their lengths. This is due to the fact, that the wedge action of the teeth or projections on each other causes the metal at said edges to yield and bring them into intimate contact, notwithstanding slight irregularities thereof, and the rounding of the teeth in the manner shown provides the necessary clearance of the teeth on each other to aiford such wedging action.

By reason of the fact that very intimate abutting contact may be secured and maintained between the toothed or serrated edges of the laminae, the magnetic permeability thus secured at the joints renders it unnecessary to interleave the laminae at the joints so as to break joints between the indivldual lfiIIllIlEB or groups of lamlnae, as has heretofore been common and necessary. This arrangement also materially reduces the time required to assemble the laminae to produce the circuit struc ture, and correspondingly reduces the cost of the same. In the manufacture of the magnetic circuit structure the laminae for the cross members are assembled as they are cut or punched with the burrs thereof all facing in one direction, while the laminae for the top and bottom members are likewise arranged with respect to each other but are reversed with respect to those of the cross members (Figure 7). This practice may be readily followed in bunching or grouping the laminae inasmuch as the laminae for the cross pieces may be assembled on the punch press without reversing them, while the laminae for the top and bottom members will be reversed, the work not entailing any special observation or inspection on the part of the person assembling the laminae.

A further advantage of making the sawgal pieces symmetrical with respect to dimensions, shape and location, in addition to the fact that they are thereby rendered in-* terchangeable, is that both ends of each cross piece laminae may be cut in a single operation of a suitable die. A die suitable for thus cutting the saw-tooth projections may be formed with an intermediate hold down plate-to hold the laminae fixedly on a flat support and two dies which are adapted to simultaneously act on the ends of each laminae or plate to cut' the sawtooth projections.

I claim as my invention:

1. A lamina-ted magnetic circuit structure comprising laminated members, the

laminae of each of which members have N edges to thereby increase the magnetic jointrelatively to the cross-section of the abutting laminae5'together ,with means acting on the laminae in the direction of their planes to force said'joints into close abutting engagement.

3. A laminated magnetic circuit structure for transformers comprising a top member, a. bottom member and cross members, the laminae of said cross members abutting with said other members along transversely continuous straight edges, each composed of a plurality of fine pitch sawtooth projections and complementary indentations on said abutting member.

4. A laminated magnetic circuit structure for transformers comprising a top 5 member, a bottom member and cross members, the' laminae of said cross members abutting with said other members along transversely continuous straight edges, each composed of a plurality of fine pitch sawtooth projections and intervening indentations symmetrical With respect to a median line therethrough.

5. A laminated magnetic circuit structure for transformers comprising a top member, a bottom member and cross members, said cross members being provided with a plurality of fine pitch saw-tooth projections, disposed symmetrically with respect to a median line therethrough, and the top and bottom members being provided along their proximate edges with V-shaped depressions complementary to said sawtooth projections.

6. A laminated magnetic circuit structure for transformers comprising a top member, a bottom member and cross members, said. cross members being provided with a plurality of saw-tooth projections disposed symmetrically with respect to a median line therethrough and the top and bottom members being provided along their proximate edges with sunkenQV-shaped depressions complementary to said saw-tooth projections, the angularity of said sawtooth projections and corresponding depressions being substantially sixty degrees with respect to said median line, as and for the purpose set forth.

7 A laminated circuit structure for transformers comprising a. top member, a bottom member and 'cross members, the laminae of the cross members abutting at their ends with the laminae of the top and bottom members along broken edges of sharp angle saw-tooth formation, and the laminae of the top and bottom members being cut away opposite to said broken edges to partially receive a clamping bolt arranged to prevent displacement of the laminae in'their planes i 8. A laminated circuit structure for transformers comprising a top member, a

bottom member and cross members, the.

laminae of the members abutting at their ends with the proximate edges of the laminae of the top and bottom members along non-overlapping broken edges of sharpr a-ngle saw-tooth formation, clamping means to confine the laminated structure in assembled position, and wedge means to force the saw-toothed abutting edges of the laminae together.

9. A laminated circuit structure for transformers comprising a top member, a bottom .member and cross members, the laminae of the cross members abutting at their ends with the laminae of the top and bottom members along broken lines of extended acutely angled saw-tooth formation, a framefor said circuit structure, clamplng bolts associated With the frame for conv fining the laminated structure in assembled position, and Wedgmg means between said bolts and the outer edges .of the top and bottom member laminae, acting-in the direction of the axes of said sawteeth to force the saw-tooth abutting edges of the laminae together.

10. In a laminated circuit structure for transformers, a lamina or plate provided on one edge and Within the line of said edge with a series of acutely angledsnnken depressions and intervening tooth-like projections, and rovided at its opposite edge with a clamping bolt receiving recesses.

11. A laminated magnetic circuit structure comprising laminated members, the laminae of which have abutting contact along irregular lines composed of a plurality of symmetrical Saw-tooth projections,

on one hand, engaging a series of indentations on the other hand to thereby enlarge the magnetic joint relatively to the crosssection of the abutting laminae, the said projections being made less sharp than the bottom angles of the indentations, for the purpose set forth.

12.-A laminated transformer core comprising separately formed side and cross members, the side members formed on their proximate edges with a plurality of numerous closely spaced, acutely angled indentations, symmetrical with respectv to their dimensions and form, and the crossmembers being each provided at each end edge with a series of closely spaced like shape and dimensioned teeth to intimately interfit along their angular edges with the angular edges bounding said indentations.

13. A laminated transformer core comprising separately formed side and cross members, and side members formed on their proximate edges and within lines defining said edges with a plurality of series of closely spaced, acutely angled indentations,

symmetrically with respect to their dimenslons and form, and the cross-members being each provided at each end edge with a series of closel spaced like shaped and dimensioned teet to intimately interfit along their angular edges with the angular edges bounding said indentations.

14. A transformer core comprisinglaminated members, the laminae of WhlCh are formed on their proximate edges with nu merous closely spaced, interfitted, acutely angled projections and intervening spaces, symmetrical with respect to their dimensions and form, and with all of the projections of the laminae of each member in line, the projections of one set of laminae engaging the faces of said intervening spaces of another set of laminae.

15. A transformer core comprising laminated members, the laminae of which are formed on their proximate edges with numerous closely spaced, interfitted equilateral projections and intervening spaces,

symmetrical with respect to their dimensions and form, and with all of the projections of the laminae of each member in respective lines to produce laminated members presenting a uniform series of transversely aligned indentations and rows of transverse projections.

16. A transformer core, comprising a plurality of laminated elements, each of which is provided with one or more serrated areas presenting aligned apices, and means for assembling said elements en bloc in butt joint relationship along said serrated areas.

In testimony, that I claim the foregoing as my invention I afiix my signature in the presence of two witnesses, this 26th day of January A. D. 1916.

CHESTER H. THORDARSON.

Witnesses:

W. L. HAIL, REBBECA WILLNER. 

